Prototype Alchitry IO shield board config.

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So I don't know if this is the best way to do this, but my idea was to use "conn" as a general way to refer to the carrier.
Alchitry Cu and Au (carriers) use iCE40 HX8K and Xilinx XC7A35T respectively so their config files would look totally different. The AlchitryCuIOPlatform and AlchitryAuIOPlatform would both inherit from their carrier board.

To implement the IO board for the Au, I would just duplicate the Cu class, and change the "attr" fields to be appropriate to the XC7 chip, but leave everything else the same I think.

Is there a cleaner way to do this? It's gross, especially the dip-switches since they are spread over two connectors multiples times sequentially.

Schematic for x-reference if needed.

alchitry_io_sch.pdf